Standby Generator on Line Side of Main

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MEP Guy

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Is anyone aware of a Code provision prohibiting the installation of a Standby Generator Transfer switch on the service entrance, prior to the main circuit breaker. The transfer switch would be rated as Service entrance equipment.

Thanks for any help.
 
transfer

transfer

If the transfer switch is service rated I know of no regulations which prohibit it being installed prior to the main circuit breaker
 
MEP Guy said:
Is anyone aware of a Code provision prohibiting the installation of a Standby Generator Transfer switch on the service entrance, prior to the main circuit breaker. The transfer switch would be rated as Service entrance equipment.

Thanks for any help.
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To qualify a transfer switch as service rated, it must contain an over current device on the line side of the normal input. Otherwise you will have a violtion of article 230.94.

230.94 Relative Location of Overcurrent Device and Other Service Equipment
The overcurrent device shall protect all circuits and devices.
Rick
 
It's OK

It's OK

We've installed dozens of standby generators and transfer switches. A service rated transfer switch is always put before the main when used with pad and trailer mount generators. Only exception is for those cheap owner supplied pick-your-six-circuit jobs for portable generators.
 
Thanks

Thanks

Thanks for the response ... the ATS is being cut into the existing elec system ... any problem with locating the ATS outside (Nema 3R) and running a service ground back to the existing service entrance equipment.

Thanks again.
 
MEP Guy said:
Thanks for the response ... the ATS is being cut into the existing elec system ... any problem with locating the ATS outside (Nema 3R) and running a service ground back to the existing service entrance equipment.

Thanks again.
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I spoke with an inspector about a simular situation a few weeks ago and as an altenative method, he would like to see a grounding electrode conductor brought from the inside equipment, but it was redundant to the equipment ground ran with the feeder conductors.The main was located outside prior to the ats.This is a must.Grounds and neutrals were kept seperated after the ats.You will need to watch your main bonding location so as to not have your grounds carrying current.
Rick
 
bugzapper said:
We've installed dozens of standby generators and transfer switches. A service rated transfer switch is always put before the main when used with pad and trailer mount generators.
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The type of generator does'nt matter.What matters is that you have a main on the service conductors before the ats.It does'nt make it right that you installed dozens that way.
Rick
 
MEP Guy said:
Thanks for the reply - why is it a must to have the main before the ATS ?
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Without a main, you do not have any overcurrent protection, nor any way other that cutting the service off, to maintain, repair, or replace the switch.
Rick
 
Let me clarrify ... the ATS is rated as service entrance equipment. It will be cut in before the EXISTING main.

The new outdoor ATS will be grounded back to the existing service entrance grounds and will serve as the new service entrance.

Any code problems ?
 
Yes it has a main circuit breaker and is rated as suitable for service entrance equipment. If we install as noted before and run ground back to exisitng service entrance grounds I think we are ok.

Agreed?
 
MEP Guy said:
Agreed?
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I would agree that you need to run an equipment ground with your feeders and seperate your grounds and neutrals in the load panel.Make your main bonding jumper in the ats.If you establish a grounding electrode system out at the ats,You can look at the building as a seperate structure and bond your existing electrodes in the building to the equipment ground bar.
Rick
 
So we can just just run a seperate electrode grounding conducter from the ATS to the existing grounding system without seperating the gounds and nuetrals at the existing service entrance because this be parrallel paths to ground ?
 
If I may throw in a few tid-bits, in no particular order:

The first thing the incoming utility conductors must land on, other than the meter, is a service rated disconnect. In need not necessarily be a breaker (or fuses), as long as said OCPD is adjacent to (as in next to) the disconnect.

A service-rated transfer switch must have a disconnect at its utility input. As long as it's rated for service duty, the OCPD may be in an adjacent enclosure, and perhaps even be the original main breaker if it's next to the transfer switch.

Now, most service-rated ATS's do use breakers as the disconnect, because it's cheap and it makes the ATS more versatile, becuase it can eliminate the need for a separate OCPD. It's easier to mount a breaker than a switch.

While the OCPD may be in an adjacent enclosure, the new disconnect's enclosure is now where the GEC's and EGC's must all land, whether it's ahead of, or within, the ATS, and the neutrals and EGC's must separate in this enclosure.
 
RUWired said:
I would agree that you need to run an equipment ground with your feeders and seperate your grounds and neutrals in the load panel. Make your main bonding jumper in the ats.
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Correct.

If you establish a grounding electrode system out at the ats,You can look at the building as a seperate structure and bond your existing electrodes in the building to the equipment ground bar.
Rick
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Not correct, if the ATS is in or on the same building.
 
MEP Guy said:
So we can just just run a seperate electrode grounding conducter from the ATS to the existing grounding system without seperating the gounds and nuetrals at the existing service entrance because this be parrallel paths to ground ?
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No. As with any time an existing panel becomes a sub-panel, you must separate the neutrals from the EGC's.
 
Thanks guys. Just to be clear ... the ATS will be the new main - the ATS EGC will have bonded nuetrals and grounds and will be run back to the current service entrance grounding electrode system.

Ground and nuetral at the existing equipment (no longer the service entrance) will need to be seperated ... correct ?
 
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